1. Field of the Invention
The present invention relates to hot and cold therapy apparatus and methods. More specifically, the present invention relates to portable solid-state thermal therapeutic apparatus and methods employing heat pump heat transfer devices and a circulating working fluid to cool and warm body parts.
2. Description of the Related Art
The benefits of hot and cold therapy in treatment of various human and animal conditions are well documented. Various apparatus have been devised to achieve the desired transfer of heat between a creature, human or animal, and such an apparatus. Classic examples are the hot water bottle and the ice pack. Modern medicine now recommends specific amounts of heat transfer for specific durations of time as are indicated for various physical ailments and conditions. For example, soft tissue injuries often indicate cold therapy immediately after injury for several hours. Lower back pain can be treated with heat therapy to alleviate pain.
Traditionally, hot and cold therapy has been accomplished with the affected individual in a fixed position. Such thinking corresponded to the concept of limited physical movement of the patient during therapy or recovery from injury. However, patients often desire some degree of mobility during therapy. Movement and mobility during hot and cold therapy, generally thermal therapy, is acceptable in the case where there is no undue strain to the affected portion of the patient's body. In fact, some movement of the affected area is tolerable, and sometimes desirable. Given the need and desire for mobility during thermal therapy, some devices and apparatus have been brought to market. One example is the ice chest and bladder cold therapy system. In the ice chest system, the user carries and insulated chest that contains a mixture of ice and water, along with a pump and battery. A pair of hoses is coupled the chest and pump and to a body-worn bladder, which is held against the affected portion of the patient's body. The patient is able to carry the chest as they move about. Some significant limitations of this approach are the size and bulk of the systems vis-à-vis carrying it, and the lack of control over temperature.
Efforts to reduce the size and weight, and enhance the controllability of portable thermal therapy systems have not kept pace with the needs and desires of patients, therapists and doctors. The use of Peltier effect solid thermoelectric modules (hereinafter “TEM” or “TEM's”) has been considered, as is evident in the prior art. For example, U.S. Pat. No. 5,097,829 to Quisenberry for “Temperature Controlled Cooling System” teaches a TEM heat pump cold therapy device with a temperature control system. A circulating fluid is used with a thermal blanket. A pump circulates the fluid, and a fin type heat exchanger removes the waste heat. A pulse width modulated electrical signal powers the TEM pump to control temperature. However, the Quisenberry device is only for fixed operation, receiving substantial power input from the utility power grid.
Another reference is U.S. Pat. No. 5,174,285 to Fontenot for “Localized Heat Transfer Device.” Fontenot teaches a TEM pump cooler that employs a hermetically sealed fluid circuit and a peristaltic pump. The closed loop system prevents the working fluid from being contaminated. A reversible cassette can be changed to make it a heat therapy unit. However, the Fontenot device is also only powered from the utility grid, and is of substantial size and power consumption. Another reference is U.S. Pat. No. 5,895,418 to Saringer for “Device for Producing Cold Therapy.” Saringer teaches a TEM cooling device similar to Quisenberry, but adds a thermal reserve in the form of a tank of liquid. The physical structure of the heat exchanger is such that the device can be made somewhat smaller than the prior designs. However, Saringer is still a fixed position device, not contemplating the aforementioned desired mobility aspects. Thus it can be understood, there is a need in the art for a compact and portable thermal therapy device capable of both hot and cold therapy in such a configuration as to enable comfortable portable operation.